1. Field of the Invention
The present invention relates to a non-contact probe and a measuring machine provided with the non-contact probe.
2. Description of Related Art
There have been typically known a non-contact probe including an emitting element that radiates light and a light receiving element that receives the light radiated from the emitting element, the non-contact probe detecting an object without contact based on the light received by the light receiving element, and a measuring machine provided with the non-contact probe (see, for instance, Patent Literature 1: JP-B-7-48044).
A measuring instrument (measuring machine) for a step gauge disclosed in Patent Literature 1 includes a detector (non-contact probe). The detector includes an emitting portion (emitting element) and a light receiving portion (light receiving element). Light radiated from the emitting portion is reflected on the step gauge (object) to be measured and the reflected light is received by the light receiving portion. The detector detects a position of the step gauge to be measured based on the light received by the light receiving portion.
FIG. 5 is an illustration showing an example of spectral characteristics of the emitting element and the light receiving element. In FIG. 5, a horizontal axis represents wavelength and a vertical axis represents intensity and sensitivity.
In such a non-contact probe, as shown in FIG. 5, a spectral linewidth of a spectral-sensitivity characteristic S1 (represented by a solid line in FIG. 5) of the light receiving element is designed to be sufficiently broad as compared to a spectral linewidth of a spectral-intensity characteristic S2 (represented by a dotted line in FIG. 5) of the emitting element so that the light receiving element can receive the light radiated from the emitting element.
FIG. 6 is an illustration showing spectral characteristics of sun light. In FIG. 6, a horizontal axis represents wavelength and a vertical axis represents intensity.
Here, as shown in FIG. 6, a spectral-intensity characteristic S3 of sun light is distributed in a broad range.
Accordingly, in the measuring instrument for the step gauge disclosed in Patent Literature 1, since the light receiving portion is exposed outside, sun light and the like enter the light receiving portion to cause disturbance, so that the position of the step gauge to be measured may be erroneously detected.
In order to avoid such an erroneous detection, it is considered to increase intensity of the light radiated from the emitting element to improve an SN (Signal to Noise) ratio to the disturbance.
Alternatively, in order to avoid such an erroneous detection, it is also considered to strengthen a directional characteristic of the light receiving element to improve an SN (Signal to Noise) ratio to the disturbance.
However, in order to increase the intensity of the light radiated from the emitting element and the directional characteristic of the light receiving element, designs of the non-contact probe, a structure of the measuring machine, an electrical system and the like need to be changed. Moreover, with increasing intensity of the light radiated from the emitting element, lifetime of the emitting element is shortened.